A Data-driven Approach for Estimating Relative Voltage Sensitivity

Voltage sensitivity expresses analytically the dependency between voltage and active or reactive power. Knowing the voltage sensitivity is necessary in many power system applications, such as the Distributed Energy Resources (DER) optimal placement and control. The majority of voltage sensitivity estimation methods assume having an accurate model of the grid and only consider a balanced grid operation at the nominal point, which is not realistic. In this paper, a method based on Mutual Information (MI) is proposed, which is able to evaluate the nonlinear dependencies between two variables, in order to estimate the relative voltage sensitivity. Contrary to the existing methods, the proposed MI-based approach only requires measurements at the point of interest and does not require any grid model nor measurements from other nodes in the grid. As a use case, the optimal allocation for an Energy Storage System (ESS) in a real medium voltage network in Germany has been presented. Measurement results confirm the effectiveness of the new approach for estimating relative voltage sensitivity

Model-less Measurement-based Computation of Voltage Sensitivities in Unbalanced Electrical Distribution Networks

Within the context of microgrids optimal voltage control, most schemes proposed in the literature either rely on (i) droop-control methods or (ii) methods involving the computation of explicit nodal power set-points as a solution to a given optimization problem. The first category of approaches is in general suboptimal as it relies on locally sensed measurements. The second category guarantees some level of optimality but requires an accurate and up-to-date model of the network that is, in general, not always available in low voltage grids. To overcome the aforementioned limitations, in this work we propose a methodology suitable for voltage control in generic low voltage 3-phase unbalanced grids. It can be used for the computation of either explicit power set-points or to define the droops of local voltage regulators. Its main characteristic is that it does not rely on the knowledge of the system model and its state. In particular, the goal is to compute linearized dependencies between voltage magnitude and nodal power injections, i.e., voltage sensitivity coefficients. The proposed method assumes availability of a monitoring infrastructure and the computation of the desired sensitivities involves the solution of an over-determined system of linear equations constructed solely using available measurements of nodal power injections and voltage magnitudes. The proposed method is also capable to account for the measurement errors and their time correlation. The performance evaluation of the proposed method is carried out using real measurements coming from a real low voltage feeder located in Switzerland equipped with an appropriate metering infrastructure